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An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a higher resolving power than light microscopes and can reveal the structure of smaller objects. A scanning transmission electron microscope has achieved better than 50 pm resolution in annular dark-field imaging mode and magnifications of up to about 10,000,000× whereas most light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000×.
Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures visible without a microscope. Although one may divide microscopic anatomy into organology, the study of organs, histology, the study of tissues, and cytology, the study of cells, modern usage places all of these topics under the field of histology. In medicine, histopathology is the branch of histology that includes the microscopic identification and study of diseased tissue. In the field of paleontology, the term paleohistology refers to the histology of fossil organisms.
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the intensity of the detected signal to produce an image. In the most common SEM mode, secondary electrons emitted by atoms excited by the electron beam are detected using a secondary electron detector. The number of secondary electrons that can be detected, and thus the signal intensity, depends, among other things, on specimen topography. Some SEMs can achieve resolutions better than 1 nanometer.
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also collectively called epoxy. The IUPAC name for an epoxide group is an oxirane.
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device.
A microscope slide is a thin flat piece of glass, typically 75 by 26 mm and about 1 mm thick, used to hold objects for examination under a microscope. Typically the object is mounted (secured) on the slide, and then both are inserted together in the microscope for viewing. This arrangement allows several slide-mounted objects to be quickly inserted and removed from the microscope, labeled, transported, and stored in appropriate slide cases or folders etc.
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations.
Araldite is a registered trademark of Huntsman Advanced Materials referring to their range of engineering and structural epoxy, acrylic, and polyurethane adhesives. Swiss manufacturers originally launched Araldite DIY adhesive products in 1946. The first batches of Araldite epoxy resins, for which the brand is best known, were made in Duxford, England in 1950.
A microtome is a cutting tool used to produce extremely thin slices of material known as sections. Important in science, microtomes are used in microscopy, allowing for the preparation of samples for observation under transmitted light or electron radiation.
Ultramicrotomy is a method for cutting specimens into extremely thin slices, called ultra-thin sections, that can be studied and documented at different magnifications in a transmission electron microscope (TEM). It is used mostly for biological specimens, but sections of plastics and soft metals can also be prepared. Sections must be very thin because the 50 to 125 kV electrons of the standard electron microscope cannot pass through biological material much thicker than 150 nm. For best resolutions, sections should be from 30 to 60 nm. This is roughly the equivalent to splitting a 0.1 mm-thick human hair into 2,000 slices along its diameter, or cutting a single red blood cell into 100 slices.
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce images of very small objects.
Hydroxyethylmethacrylate or HEMA (also known as glycol methyacrylate, GMA) is the organic compound with the formula H2C=C(CH3)CO2CH2CH2OH. It is a colorless viscous liquid that readily polymerizes. HEMA is a monomer that is used to make various polymers.
The transmission electron microscope (TEM) is used as an important diagnostic tool to screen human tissues at high magnification, often in conjunction with other methods, particularly light microscopy and immunofluorescence techniques. The TEM was first used extensively for this purpose in the 1980s, especially for identifying the markers of cell differentiation to identify tumours, and in renal disease. Immunolabelling techniques are now generally used instead of the TEM for tumour diagnosis but the technique retains a critical role in the diagnosis of renal disease and a range of other conditions.
A diamond knife is a very sharp knife in which the edge is made from diamond, invented by Humberto Fernández-Morán in 1955. Diamond knives are used for medical and scientific applications where an extremely sharp and long-lasting edge is essential. The knives are very expensive to purchase, depending on the quality and size of the knife; in addition the knives must be professionally sharpened as the edge dulls.
Immunogold labeling or Immunogold staining (IGS) is a staining technique used in electron microscopy. This staining technique is an equivalent of the indirect immunofluorescence technique for visible light. Colloidal gold particles are most often attached to secondary antibodies which are in turn attached to primary antibodies designed to bind a specific antigen or other cell component. Gold is used for its high electron density which increases electron scatter to give high contrast 'dark spots'.
Serial block-face scanning electron microscopy is a method to generate high resolution three-dimensional images from small samples. The technique was developed for brain tissue, but it is widely applicable for any biological samples. A serial block-face scanning electron microscope consists of an ultramicrotome mounted inside the vacuum chamber of a scanning electron microscope. Samples are prepared by methods similar to that in transmission electron microscopy (TEM), typically by fixing the sample with aldehyde, staining with heavy metals such as osmium and uranium then embedding in an epoxy resin. The surface of the block of resin-embedded sample is imaged by detection of back-scattered electrons. Following imaging the ultramicrotome is used to cut a thin section from the face of the block. After the section is cut, the sample block is raised back to the focal plane and imaged again. This sequence of sample imaging, section cutting and block raising can acquire many thousands of images in perfect alignment in an automated fashion. Practical serial block-face scanning electron microscopy was invented in 2004 by Winfried Denk at the Max-Planck-Institute in Heidelberg and is commercially available from Gatan Inc., Thermo Fisher Scientific (VolumeScope) and ConnectomX.
Fritiof Stig Sjöstrand was a Swedish physician and histologist born in Stockholm. He started his medical education at Karolinska Institutet in 1933, where he received his Ph.D. Karolinska Institutet in 1944. Sjöstrand worked as an assistant at the department of pharmacology, where he first had used polarization microscopy, he first heard about the new method of electron microscopy in 1938, within which he would become a pioneer. Manne Siegbahn at the Nobel Institute for Physics had planned to build an electron microscope in Sweden, and Sjöstrand got involved in the project to explore its use in medical research. The main challenge was to produce sufficiently thin samples, and Sjöstrand's method for producing ultrathin tissue samples was published in Nature in 1943. However, it seemed that research based on electron microscopy would be too time-consuming for a Ph.D. thesis, so his 1944 thesis was based on fluorescence spectroscopy. In 1947-1948, he received a scholarship to further study electron microscopy at Massachusetts Institute of Technology's Department of Biology. Back in Sweden, he received funding to build up an electron microscopy research laboratory. In 1959, Sjöstrand was both offered a position as professor of histology at Karolinska Institutet, and as professor at University of California, Los Angeles (UCLA). He chose UCLA, because conditions for research and funding were better there.
Dr. Manfred E Bayer was a medical doctor and a microscopist, best known for his research in bacterial and viral infrastructure using electron microscopy. He was the first person to visualize yellow fever virus in cultured cells and to obtain ultra-thin sections of the cell wall of E. coli by penicillin.
Microtechnique is an aggregate of methods used to prepare micro-objects for studying. It is currently being employed in many fields in life science. Two well-known branches of microtechnique are botanical (plant) microtechnique and zoological (animal) microtechnique.
Fossil preparation is the act of preparing fossil specimens for use in paleontological research or for exhibition, and involves removing the surrounding rocky matrix and cleaning the fossil.
References
- ↑ Stäubli, W. (1963). "A new embedding technique for electron microscopy, combining a water-soluble epoxy resin (Durcupan) with water-insoluble Araldite" (PDF). The Journal of Cell Biology. Rockefeller Univ Press. 16 (1): 197–201. doi:10.1083/jcb.16.1.197. PMC 2106182 . PMID 13978678.
- ↑ Kushida, H. (1963). "A Modification of the Water-miscible Epoxy Resin "Durcupan" Embedding Method for Ultrathin Sectioning". Journal of Electron Microscopy. Japan Society Microscopy. 12 (1): 72–73. doi:10.1093/oxfordjournals.jmicro.a049375. Archived from the original on 2013-04-15.
- ↑ "Durcupan recipe". Cold Spring Harbor Protocols. 2011: pdb.rec12381. 2011. doi:10.1101/pdb.rec12381.
- ↑ Punge, A. (2009). Polymer embedding for ultrathin slicing and optical nanoscopy of thick fluorescent samples. Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität zu Göttingen. pp. 34–35. Archived from the original on 2017-06-22.